Clinical-endoscopic parameters of UC presentation were studied in 1705 out-patients, observed consecutively in 17 Italian gastroenterology centers (males 60.2%; average age at diagnosis 38.5 +/- 16.4 years), and were subdivided arbitrarily into quartile age groups at diagnosis (0-25, 26-35, 36-50, >50). A significantly greater prevalence in males, increasing with age, was shown at diagnosis (P = 0.0002), which seems to correlate with the condition of being an ex-smoker, most frequently found in males. The greater frequency of exsmokers could also, in part, justify the second peak of incidence in old age. Greater colitis extent, greater clinical activity, and greater use of steroids as the first therapeutic step are shown to prevail among younger patients and among women (P = 0.02 and P = 0.019, respectively). The same is observed for symptoms mainly representing clinical severity such as diarrhea, fever, and weight loss (P = 0.004; P = 0.006; P = 0.009, respectively). This study confirms the UC risk factor represented by the condition of being an ex-smoker and shows a greater severity of illness on diagnosis in younger patients.